I once took the late second runnings from a neighbor's Wee Heavy (he had fly sparged all he needed and was going to just dump the grains). I just added a little DME and had a nice 60 Shilling Scottish Ale in the end, so I split the batch with him and he was quite pleased. I haven't done another since, but I keep it in the back of my mind, because I brew lighter ABV beers and my neighbors usually make the big boys once in a while.